1. Field of the Invention
The present invention relates to a video signal converting apparatus for converting a video signal by 40 laced scanning into a video signal by sequential scanning, and more particularly to a video signal converting apparatus for subjecting the video signal by interlaced scanning to scanning line converting processing suited to the case where it is a telecine-converted video signal created from the screening film by the 2-3 pulldown system.
2. Description of the Related Art
A video signal conversion technique is well known, which converts a video signal from a screening film into a video signal in a standard television system such as an NTSC system, and reproduces the converted video signal as well as a video signal in an ordinary television system.
In the screening film, a spatial image is sampled as 24 frames per second, whereas in the NTSC system, the spatial image is sampled as 30 frames per second (60 fields per second). Since both adopt different sampling systems, the video signal obtained from the screening film is once telecine-converted by the 2-3 pull-down system to provide a video signal suited to the standard television system such as the NTSC system.
In order to make the telecine conversion by the 2-3 pull-down system, first, the screening film is read/scanned to create the video signal by the sequential scanning which is synchronous with the frame frequency of 24 Hz. In this case, the first frame of the screening film is caused t-o correspond to the first and second fields, the second frame is caused to correspond to the third to fifth fields, the third frame is caused to correspond to the sixth to seventh fields, the fourth frame is caused to correspond to the eighth to tenth fields. Likewise, the remaining frames are also caused to correspond to the fields. Additionally, the fifth field of the standard television system is caused to have the same image contents as those of the third field and the eighth field is caused to have the same image contents as those of the fifth field. Likewise, the remaining fields are also repeated.
In this way, in the 2-3 pulldown system, the telecine conversion is made in such a manner that the two frames of the screening film are caused to correspond to the five fields in the standard television system and according to the frame advance of the screening film, the two fields and the three fields in the standard television system are repeated alternately.
As described above, since the third filed and the fifth field, and the eighth field and tenth field have the same image contents, the inter-frame difference between the fifth field and tenth field is zero. Such a relationship occur severy five fields. Specifically, the absolute value of the inter-frame difference is integrated for a single field and the integrated value is compared with a prescribed threshold value. If the integrated value is larger than the threshold value, it is decided to be xe2x80x9cmoving (dynamic) filedxe2x80x9d, and in the other cases, it is decided to be xe2x80x9cstill (static) fieldxe2x80x9d. Thus, in the video signal converted by the 2-3 pulldown system, the still field occurs every five fields in an arithmetic progression.
Using such a characteristic, it is determined whether or not the video signal telecine-converted by the 2-3 pulldown system is included in the video signal in the standard television system, and the former is discriminated from the latter. On the basis of the result of determination, the video signal in the sequential scanning is created from the video signal by the interlaced scanning.
However, in the above conventional discriminating method, the video signal in the standard television system cannot be quickly discriminated from the telecine-converted video signal so that it takes a long time to create the video signal by the sequential scanning from the video signal in the interlaced scanning.
Specifically, in the above conventional discriminating method, the integrated value which is acquired by integrating the absolute value of the inter-frame difference over a single field is compared with a prescribed threshold value, and such processing is repeated over plural fields to detect a periodic pattern of the telecine-converted image. On the basis of this detection result, the video signal in the standard television system is discriminated from the telecine-converted video signal.
Therefore, it lakes a long time to make the discriminating processing. For example, it was difficult to prevent quickly degradation of the reproduced image by, for example, quickly detecting the switching point between the telecine-converted video signal and the ordinary video signal, or quickly detecting a change in the editing point of the video signal once edited. There was also a problem that the discriminating method must be changed according to the detected periodic pattern.
The present invention has been accomplished in order to overcome the problem of the above conventional technique. An object of the invention is to provide a video signal converting apparatus which can quickly and suitably make the switching of scanning line interpolating processing at a discontinuous position of the periodic pattern of the video signal, such as a switching point between a telecine-converted video signal and an ordinary video signal and a change in the editing point of the video signal, etc.
In order to attain the above object, the present invention provides a video signal converting apparatus for creating an interpolated scanning signal from an input video signal by interlaced scanning and interposing an actual scanning signal of the input video signal and the interpolated scanning signal between each other to create a video signal by sequential scanning, comprising:
a first detecting means for detecting a first correlation value between an interpolated field in the input video signal and a first field located one-field-period-before it;
a second detecting means for detecting a second correlation value between an interpolated field in the input video signal and a second field located one-field-period-after it;
a first deciding means for deciding whether the interpolated field is a telecine-converted video signal and deciding an interpolating method where it is the telecine-converted video signal;
a second deciding means for deciding whether or not the interpolated field is an editing point field of a film frame of one field; and
an interpolated signal creating means for setting the interpolating processing for the interpolated field at either of adaptive interpolating processing and film interpolating processing in response to the decision results of the first and the second deciding means to create the interpolated scanning signal, characterized in that
if it is decided that the interpolated field is the telecine-converted video signal on the basis of the decision result of the first deciding means, the interpolated signal creating means sets the interpolating processing for the interpolated field at the film interpolating processing to create the interpolated scanning signal; and
if it is decided that the interpolated field is the editing field on the basis of the decision result of the second deciding means, the interpolated signal creating means sets the interpolating processing for the interpolated field at the adaptive interpolating processing to create the interpolated signal.
In such a configuration, the telecine-converted video signal of a succession of film frames each having tow fields or more can be detected quickly and surely, and the editing field of the film frame of one field is subjected to suitable interpolating processing. For this reason, the display quality of the video signal by the sequential scanning can be improved which is created from the video signal by the interlaced scanning telecine-converted by the interpolating processing.
The present invention also provides a video signal converting apparatus for creating an interpolated scanning signal from an input video signal by interlaced scanning and interposing an actual scanning signal of the input video signal and the interpolated scanning signal between each other to create a video signal by sequential scanning, comprising:
a first detecting means for detecting a first correlation value between an interpolated field in the input video signal and a first field located one-field-period-before it;
a second detecting means for detecting a second correlation value between an interpolated field in the input video signal and a second field located one-field-period-after it;
a first deciding means for deciding whether the interpolated field is a telecine-converted video signal and deciding an interpolating direction where it is the telecine-converted video signal;
a third deciding means for deciding whether or not there is a movement of one dot or so per one field in the vertical scanning direction on the interpolated field; and
an interpolated signal creating means for setting the interpolating processing for the interpolated field at either of adaptive interpolating processing and film interpolating processing in response to the decision results of the first deciding means to create the interpolated scanning signal, characterized in that
if it is decided that the interpolated field is the telecine-converted video signal on the basis of the decision result of the first deciding means, the interpolated signal creating means sets the interpolating processing for the interpolated field at the film interpolating processing; and
if it is decided that there is a movement in the vertical direction on the basis of the decision result of the third deciding means, the interpolated signal creating means sets the interpolating direction in the film interpolating processing at a direction reverse to that decided by the first deciding means.
In such a configuration, the telecine-converted video signal of a succession of film frames each having tow fields or more can be detected quickly and surely, and the case where there is a movement of one dot or so per one field in the vertical scanning direction is subjected to suitable interpolating processing. For this reason, the display quality of the video signal by the sequential scanning can be improved which is created from the video signal by the interlaced scanning telecine-converted by the interpolating processing.